Gas burner control system



1938- v. G.-VAUGHAN 2,125,473

GAS BURNER CONTROL SYSTEM Filed June 18, 1936 Patented Aug. 2," 1938 PATENT? OFFICE GAS BURNER CONTROL SYSTEM Victor G. Vaughan, Attlehoro, Mass., assignor, by mesne assignments, to Metals & Controls Corporation, Attleboro, Mass., a corporation of Massachusetts Application" June 18, 1936, Serial No. 85,859

6 Claims. (C1. 158-11'l.1)

This invention relates to gas burner control systems, and with regard to certain more specific features, to safety gas burner control systems.

Among the several objects of the invention may be noted the provision of a control system of the class described for gas burners, in which highly efflcient safety provisions are made to prevent the escape of unignited gas from the system; the provision of a system of the class described embodying electrical ignition means for the gas burner; the provision of a system of the class described which is not readily aifected by clogging of the gas burner orifices, whereby it is rendered more certain in operation over long periods of time without periodic cleaning; and the provision of a system of the class described which is relatively simple and economical in construction. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

The accompanying drawing is a diagrammatic representation of a system embodying the present invention.

Referring now more particularly to the drawing, numeral l indicates a main gas supply pipe, in which is provided a main shutoff valve or cock 2. Numeral 3 indicates the casing of a diaphragm or similar type pressure-actuated electric switching arrangement. This unit, which will hereinafter be called a pressure balance switch, has upper and lower compartments 6 and 5, respectively, separated by a gas-tight flexible partition or diaphragm 9. Attached to the diaphragm 6 is a switch push rod l, which cooperates with and actuates contact arms 8 and 9 in a transformer pri'mary electrical circuit it, connected with a suitable power source. A gas conduit I l connects the lower compartment 5 of the pressure balance switch to the main gas line i Beyond, that is, to the right of the connection it in the main gas line i there is provided a thermostatic valve 02. The valve l2 includes a seat l3, a closure element Hi, a valve stem l5 operating the closure element it, and a thermostatic disc orplate it operating the other end of the valve stem 85. The thermostatic disc or plate is may, for example, be of the type shown in John A. Spencer Patent 1,448,240, dated March 13, 1923, or it may comprise a radially corrugated, snapacting thermostatic disc of the type shown in John A. Spencer Patent 1,895,591, dated January 31, 1933. The thermostatic disc I6 is mounted at its periphery in a housing ll, which is supported on a tube l8 forming an extension of the casing of the valve l2. The housing I! and tube I8 are gas-tight with the valve l2.

A characteristic of the thermostatic disc I 6 is that it has two positions of relative stability, represented by oppositely concave positions, and intermediate positions of instability, which stable positions are assumed in response to predetermined ambient 'temperature values. The disc housing I 1 acts as a conductor of heat to and from the disc I6, by means of the periphery of the disc. When the disc 5 is cold, and thus in its downwardly conical or concave position, its reaction on the stem I5 causes the valve closure I4 to seat upon the seat I 3, but when the disc I6 is hot, and thus upwardly conical or convex, it lifts the valve closure l4 01f the seat I3, thus opening the valve l2.

Numeral I9 indicates a connection that is made from the upper chamber 4 of the pressure balance switch 3 to the main gas line I at a point beyond, or to-the right of the thermostatic valve l2. Located in connection I9 is orifice 30, which is shown for convenience as an adjustable needle valve.

Numeral 20 indicates a transformer, the primary 2| of which is in series with the switch blades 8 and 9 in the electrical circuit [0. Numeral 22 indicates the secondary of the transformer 29, which is connected by buss wires 23 and 24 to a radiant heater element 25, positioned above the casing ll of the thermostatic disc 16. The character of the transformer 20 is such that an alternating current voltage of the order of volts, or 220 volts, or the like impressed on the primary 2i, is transformed in the secondary 22 to a relatively low voltage, such as the order of 10 volts or the like. This provides relatively large currents in the secondary circuit, comprising the secondary winding 22, the wires 23 and 24, and the heater 25.

As will be pointed out hereinafter, the heater 25 is periodically exposed to air at incandescent temperatures, and to the effects of an open pilot flame as well. The heater 25 should accordingly be chosen so that it will not too readily oxidize. It is preferable to use the largest diameter wire possible for this heater, because the larger its diameter, the smaller the proportion of oxide (which forms on its surface) to its cross sectional area. In other words, it is possible to run the temperature considerably higher in a wire of large diameter, with less danger from deterioration than it is in a wire of relatively small diameter. The bass wires 23 and 24 are of course of suitable diameter to carry the rather large currents employed.

Numeral 26 indicates a gas pilot burner, which is connected by a gas conduit 21 to the main gas line I at a point beyond, or to the right of the thermostatic valve I2. The pilot burner 26 is so arranged that gas issuing from it can be ignited by the incandescent heater 25, and when ignited,

its flame supplies continued heat to the housing H of the thermostatic disc I6, as well as an igniting or pilot flame in the vicinity of a main burner 26, which is provided at the end of the main gas line I.

Numeral 29 indicates a thermostatic valve which is customarily provided in burner circuits of this type, and which serve to control the supply of fuel passing from the main gas line I to the burner 26 in accordance with the temperature demand upon the burner. The thermosatic valve 26 is not ordinarily a functional part of the control system of the present invention.

.The operation of the burner control system as thus described is as follows:

It is initially assumed that the cock 2 is turned ofl, so that no gas is flowing in the portion of the main gas line I beyond said cock 2. To commence operation,then, the cock 2 is turned to an open position, preferably to a wide open position. Thermostat 29 is set at the desired temperature value. The opening of cock 2 permits gas under line pressure to fill the system as far as the thermostatic valve I2, which is closed because the thermostatic disc I6 is in its cold position. Thus, line gas pressure is admitted to the lower compartment 5 of the pressure balance switch 3, and exert's a force on the flexible partition 6. As there is only atmospheric pressure in the upper compartment 4, flexible partition 6 yields to the force, and moves upwardly. Its upward motion is transmitted through the push rod I to the switch contacts 6 and 9, closing the transformer primary circuit Ill. The transformer secondary circuit is consequently energized, and the radiant heater begins to heat.

In time, the disc housing I1 absorbs and conducts sufflcient heat from the heater 25 to the thermostatic disc I6 to cause said thermostatic disc to move from its cold to its hot position. The constants of the system are so designed that a temperature of incandescence is ordinarily reached by the heater 25 before the disc I6 responds.

The response of the thermostatic disc I6, by moving to its hot position, is accompanied by an unseating of the closure I4 from the valve seat I2, thus opening the valve I 2. Thus, gas is admitted to and flows from the pilot burner 26, and at the same timethe gas pressure is transmitted at a value higher than atmospheric to the upper compartment 4 of the pressure balance switch 3, through line I9. However, because of the restriction of orifice 30 the action is-delayed somewhat after the opening of valve I2. The flexible partition 6 lowers to a balanced position in due time, however, thus opening the contacts 6 and 9 and discontinuing the flow of electric current to the transformer 20. The purpose of delaying the opening of the contacts 6 and 9 is to prolong the period of incandescence of heater 25 in the presence of gas issuing from pilot burner 26. At this point, either of two things can happen: (1) the pilot burner 26 will ignite or (2) the pilot burner 26 will not ingite.

In the first event, the incandescent heater 26 causes ignition of the gas at the pilot burner 26. The pilot burner 26, as has been described, provides an open flame in the proximity of the main burner 26, which then ignites. At the same time,

the flame-at the pilot burner 26 provides sufflcient heat to the casing I1 to maintain the thermostatic disc I6 in its hot position, thus maintaining the valve I2 open. Thereafter, as

its response to temperature conditions as aflected by the main burner 28.

If, now, the cock 2 is closed, the gas supply is cut off, causing the pilot burner 26 and the main burner 28 to extinguish, soon after which the disc housing I! and the disc I6 cool sufllciently to cause the thermostatic disc I6 to move back to its cold position, thus closing valve I2. In this manner the system resets itself for a repetition of the cycle just described.

If for any reason, upon the discontinuance of the energization of the transformer 20 (when the pressure balance switch 3 opens the transformer primary circuit), the pilot burner 26 fails to ignite from the heater 25, gas flows through the valve I2 only until the disc housing I1 and disc I6 cool to the temperature at which the disc I6 moves to its cold position. When the disc I6 moves to its cold position, the'valve I2 closes, and the system is back in its initial position.

roviding the cock 2 is left open, successive attempts at ignition will occur in the manner described. Heater 26 must reach incandescence, however, in order to cause valve I2 to open, thus if'heater 26 fails in any manner, the valve I2 remains closed and no gas escapes from the system. The only flow of unburned gas from the main burner 28 would be during the relatively short period between the moving of the thermostatic disc I6 from its hot to its cold position when the pilot burner failed, to ignite from incandescent heater 25.

The advantages of the system as thus provided are many. One of the principal advantagesis thatthe primary ignition is supplied by electrical means rather than by gas means. In prior systems where primary ignition has been supplied by a constantly burning pilot burner, included in the same gas system, trouble has frequently been experienced in that the orifice of the primary igniting pilot has been made very small purposely to conserve pilot gas consumption, and has frequently clogged with the accumulation of grease from the cooking of foods and particles of dirt in the air. The failure of the primary ignition pilot would mean the failure of the entire gas system. However, in the present invention, the electrical primary ignition control eliminates any danger from this cause.

A further advantage of the system as thus provided, is that if any part of it fails, it always fails safe. For example, as has been pointed out, gas cannot flow from the pilot or main burner until '-the thermostatic valve opens, and for this valve to open, the electric radiant heater must reach incandescence. Thus, if there were a failure in the pressure balance switch, wiring, transformer, or incandescent heater, the thermostatic valve could not open, and the system would fail safely. accidentally extinguish, the pilot would immediately reignite it, or, if the pilot should also ex- Similarly, if the main burner should i tinguish, the thermostatic valve would soon snap shut and prevent the escape of gas.

Still a further advantage of the present; invention is the manner in which it is susceptible of being used in connection with further auxiliary controls. For example, if an electrical time switch is placed in the transformer primary circuit ID, the main burner can be turned on at predesignated times. Thus, where the system is employed in a cooking oven, for example, food may be placed in the oven considerably in advance of the time in which it will be wanted. The cock 2 may then be opened wide and the full automatic control of the system relied upon for turning on the main burner 28 at the desired time. By also incorporating a motorized valve or solenoid valve of any of the well known types in the system, the burner can be turned ofi at a still more future desired time.

The apparatus of the invention as shown in the accompanying drawing is entirely diagrammatic. In practice, the pressure balance switch 3, the valve I2, the heater 25, the pilot burner 26, and orifice 30 can all be incorporated into a unitary structure with a consequent resulting simplicity of arrangement.

In view of the above, it will be seen that the.

several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a gas burner control system, a main gas feed line, a main burner, a thermostatically operated valve in said main gas line, a pilot burner positioned so as to be capable of igniting said main burner and also to heat said thermostatic valve, electrical heating means in position to heat said thermostatic valve, and also to ignite said pilot burner, and a balanced pressure switch adapted to operate said electrical heating element, said balanced pressure switch comprising a movable member subjected on its two sides respectively to gas pressure from the opposite sides of said thermostatic valve.

2. In a gas burner control system, a main gas feed line, a main burner, a thermostatically operated valve in said main gas line, a pilot burner positioned so as to be capable of igniting said main burner and also to heat said thermostatic valve, electrical heating means in position to heat said thermostatic valve, and also to ignite said pilot burner, and a balanced pressure switch adapted to operate said electrical heating element, said balanced pressure switch comprising a movable member, pressure chambers on each side of said member, and connections respectively from each of said chambers to the main gas line on opposite sides of the thermostatic valve, one of said connections having a bleed orifice therein, whereby said member moves in accordance with a delayed gas pressure difierential on the opposite sides of said thermostatic valve.

3. In a gas burner control system, a main gas feed line, a thermostatically operated valve in said main gas feed line, a pilot burner connected to said main gas feed line beyond said thermostatic valve, and adapted to supply heat to said thermostatic valve, an electric heater likewise adapted to supply heat to said thermostatic valve, a circuit for supplying said electric heater with power, and a switch in said circuit, and means for closing said switch when said thermostatic valve is closed and opening said switch when said thermostatic valve is open, said last-named means comprising a balanced pressure switch operating upon the differential pressure in said main gas feed line ahead of and beyond said thermostatic valve, said pressure switch comprising a casing having two chambers separated by a flexible diaphragm, means connecting one of said chambers to the main gas feed line ahead of said thermostatic valve, and means connecting the other chamber to said main gas feed line beyond said thermostatic valve.

4. In a gas burner control system, a main gas feed line, a thermostatic valve in said main gas feed line, a pilot burner positioned to influence the operation of said thermostatic valve, and electrical ignition means for said pilot burner, said electric ignition means likewise being positioned to influence the temperature of said thermostatic valve, and means for controlling the operation of said electrical ignition means comprising a casing, a flexible diaphragm dividing said casing into two chambers, means connecting one of said chambers into the main gas feed line on one side of the thermostatic valve, and means connecting the other chamber to the main gas feed line on the other side of said thermostatic valve, said second connecting means providing a restriction to the immediate balancing of pressures in said chambers, and electrical switching means associated with the flexible diaphragm for movement therewith.

5. A system as set forth in claim 1, in which the thermostatic valve includes, as the actuating element thereof, a snap-acting thermostatic disc.

6. A system as set forth in claim 1, in which the thermostatic valve includes, as the actuating element thereof, a snap-acting thermostatic disc, and means mounting said disc and likewise conducting heat to said disc from said pilot burner and said electrical heating means.

- VICTOR G. VAUGHAN. 

